Effect of Agro-Industrial Effluents on Soil Fertility, Pore Size Architecture, and Hydraulic Properties of Tropical Soils with Contrasting Parent Materials

Abstract

This study evaluated the effects of palm oil mill effluents (POME) and cassava mill effluents (CME) on the physical characteristics, chemical properties, and fertility status of soils derived from diverse parent materials, namely Coastal Plain Sands (CPS), Beach Ridge Sands (BRS), and Sand Stone/Shales (SSS). A total of 108 composite soil samples were collected from effluent-treated and control soils. All statistical analyses were conducted using SPSS Version 31. Results showed that effluent application improved key soil chemical characteristics compared with control soils. POME improved soil conditions by reducing acidity to near-neutral levels (6.89 to 6.71 in CPS, 5.74 to 5.71 in BRS, and 6.37 to 6.53 in SSS), increasing organic carbon and exchangeable bases (10.46, 9.48, and 10.03 cmol kg-1 for CPS, BRS, and SSS, respectively), and improving effective cation exchange capacity (13.66, 12.54, and 13.50 cmol kg-1 for CPS, BRS, and SSS, respectively). CME also improved soil nutrient status, but its effects on soil properties varied by soil type and depth. Effluent-treated soils demonstrated higher nutrient availability and improved structural properties, as indicated by decreased bulk density (1.24 ± 0.04, 1.55 ± 0.10, and 1.39 ± 0.09 g cm-3), increased porosity (57.07, 56.70, and 55.53%), enhanced moisture content (CV of 80.67, 59.51, and 37.90%) for CPS, BRS, and SSS, respectively, and improved hydraulic conductivity (with minimum and maximum values of 0.15 to 1.23 cm hr-1 accross all 3 parent materials). These findings demonstrate that agro-industrial effluents enhance nutrient availability and soil quality in tropical sandy soils, with POME showing stronger soil improvement potential. This study highlights the potential reuse of agro-industrial wastes as sustainable soil amendment materials in tropical environments.